I watched a programme on this the other night, it was supposedly signed at Runnymede, by King John, who couldn't write so he just had to put a cross. There seems to be some doubt now about whether or not the document did actually ever go near Runnymede, or whether it  may have actually been drafted later.

That aside I was taught in history that it was signed by King John and the Barons of England at Runnymede on 15th June 1215.

As to how many of its clauses are still law today, I don't know I need to research  

Is it 3 ?

Clause 1. The liberties of the Church of England

Clause 13.  The privileges of the City of London

Clause  39/40. The right to trial by Jury.

I think I heard it was only sealed as well John, there is also doubt whether the king was actually there, but we'll never know for sure being as we weren't there 

I'll have a think and be back. 

OK here we go.

I originally appear on 16th century maps of London as land to the East of present day Whitehall.

What am I ? 

Thanks.

 What is the name of the large town where there is a gigantic amusement centre about the size of five aeroplane hangars? It’s about a 90 minutes drive from London. You can try your hand at skiing, snowboarding or make a snowman. You can go indoor skydiving, rock climbing or tenpin bowling or see a movie. There are restaurants and a gym and a casino, and shops selling snow gear and active-wear.